Gene correction in S-phase-injected human embryos

Schematic of MYBPC3^∆GAGT gene targeting by injection of CRISPR-Cas9 into human zygotes at the S-phase of the cell cycle. MII oocytes were fertilized by sperm from a heterozygous patient with equal numbers of mutant and wild-type spermatozoa. CRISPR-Cas9 was then injected into one-cell zygotes. Embryos at the 4- to 8-cell stage were collected for genetic analysis. Injection during S-phase resulted in mosaic embryos consisting of non-targeted mutant, targeted NHEJ-repaired and targeted HDR-repaired blastomeres.